Gapped magnetic core structures



P 1957 J. A. BOCK ETAL GAPPED MAGNETIC CORE STRUCTURES Filed March 15, 1965 Q WW a m w wm VAm .O mnw m AA MT M B 2% H I G I United States Patent M 3,316,515 GAPPED MAGNETIC CORE STRUCTURES John A. Bock and Theodore R. Specht, Sharon, Pa., assiguors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 15, 1965, Ser. No. 439,535 3 Claims. (Cl. 336--100) This invention relates in general to magnetic core structures for electrical inductive apparatus, and more particularly to magnetic core structures having air gaps in the magnetic circuit.

Certain types of electrical inductive apparatus, such as iron core reactors, utilize a magnetic core structure having one or more non-magnetic or air gaps in the magnetic circuit, in order to achieve predetermined electrical characteristics. The gapped magnetic core structure produces higher sound levels than a similar ungapped structure, however, presenting a diflicult problem to the designer of such apparatus. This problem is becoming acute, due to more stringent sound specifications imposed by electrical utilities, who among other things, are using iron core reactors in residential areas to offset the capacitive effect of underground shielded cable systems during light load periods.

Copending application Ser. No. 283,052, now abandoned, filed May 24, 1963, by J. G. Ford et al., and assigned to the same assignee as the present application, teaches the use of an adhesive or resin disposed between the ends of the stacked magnetic laminations and the insulating spacer member Which establishes the gap. This procedure has been very effective in reducing the sound level of reactor ratings up to approximately 600 kva. When the same procedure is utilized on larger reactors, however, the same low sound levels are not obtainable, and difficulties are experienced in maintaining the adhesive seal during assembly of larger reactors. It is, therefore, desirable to provide a new and improved magnetic core structure for iron core reactors which will reduce their sound levels to within allowable limits on ratings over 600 kva., as well as on smaller reactors.

Accordingly, it is an object of this invention to provide new and improved industive apparatus which has one or more non-magnetic gaps in the magnetic circuit.

Another object of the invention is to provide a new and improved magnetic core structure for inductive apparatus which has non-magnetic gaps in the magnetic circuit.

A further object of the invention is to provide a new and improved magnetic core structure for iron core reactors which is efiective in reducing the sound level of reactors having ratings over 600 kva., as well as on smaller rated reactors.

Another object of the invention is to provide a new and improved magnetic core structure for iron core reactors which reduces the noise produced at the air gaps in the reactor.

Briefly, the present invention accomplishes the above cited objects by providing a new and improved insulating gap spacer for iron core reactors, which establishes and maintains the desired non-magnetic gap, maintains all of the laminations in each stack in the desired assembled relation, and yet allows the stacked laminations to be tightly clamped. The sound level of iron core reactors may be substantially reduced by increasing the rigidity of the stacks of assembled laminations which make up the magnetic circuit. The function of the non-magnetic, non-metallic gap spacer is to provide the desired gap distance in the magnetic circuit to produce predetermined electrical characteristics, and support the laminations in the assembled stacks to prevent them from slipping out of the desired assembled relation. The present practice is to make the gap spacer out of rectangularly shaped 3,316,515 Patented Apr. 25, 1967 electrical insulating material, with dimensions which will support each lamination and provide the desired gap dis tance. Lock plates are disposed on opposite sides of the laminations, and an opening is provided through the laminations and lock plates, through which a bolt may be inserted which is used to draw the laminations into a rigid. assembly. It has been found, however, that with the conventional spacer member, when the bolts are tightened, very little pressure may be placed on the lamina tions, resulting in stacks which are not rigid and hence produce a high sound level. If the spacer members are formed undersized, in an attempt to allow the force produced by the clamping means to apply pressure directly to the laminations, some of the laminations in the stack may be unsupported, allowing them to slip out of the desired assembled relation.

This invention accomplishes the function of holding all of the laminations in assembled relation, and allows the clamping means or bolts to exert pressure on the stacked laminations, by utilizing a spacer member which is dimensioned to support all of the laminations, but which will yield to the force produced by the clamping means to allow the clamping means to transmit or apply pressure to the stacked laminations, without changing the non-magnetic gap distance. The gap spacers may be formed of the same material as conventional gap spacers, but they are formed in a configuration which allows them to decrease their dimension in a predetermined direction, when subjected to a clamping force in this direction. The gap spacers thus flex when the clamping means applies a clamping force to the stacked laminations, to allow the clamping force from the clamping means to be applied to the laminations, producing a rigid magnetic core assembly which has a substantially lower sound level than magnetic core structures which utilize the conventional solid rectangular gap spacers.

Further objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a perspective view, partially cut away, of an iron core reactor constructed according to the teachings of the invention;

FIGS. 2 and 3 are plan and end views, respectively, of the gap spacer shown in FIG. 1;

FIG. 4 is a sectional view taken through a magnetic core, showing how gap spacers may be disposed on magnetic core structures which utilize lock plates disposed throughout the laminations at predetermined intervals, as Well as lock plates which are disposed at opposite ends of the laminations; and

FIGS. 5. and 6 are plan and end views of the gap spacers shown in FIG. 4.

Referring now to the drawings, and FIG. 1 in particular, there is shown in perspective, an iron core reactor 10, partially cut away to illustrate the teachings of the invention. In general, iron core reactor 10 includes a magnetic core structure 12, which has winding leg members or portions 14, 16 and 18 disposed in spaced parallel relation, and connected with yoke portions 20 and '22. Electrical windings, such as electrical winding 24, are disposed in inductive relation with each of the winding legs 14, 16 and 18, with only one electrical winding 24 being shown in FIG. 1 for purposes of simplicity.

The various yoke and leg members 20, 22, 14, 16 and 18 are all formed of stacked magnetic laminations 26, formed of a suitable grain oriented magnetic strip material such as silicon stcel, which has a preferred direction of easier magnetization which coincides with the longitudinal dimension of its associated leg member. Magnetic material having a second preferred direction of easier magnetization, transverseto the first mentioned direction of easier magnetization, may also be utilized. Any suitable joint design may be used to magnetically and mechanically connect the various leg portions 1 4, 16 and 18 with the yoke portions 20 and 22. Clamping means, such as channel members 19 and 21 may be utilized to hold the complete magnetic core structure 12 in assembled relation.

The various leg portions 14, 16 and 18 all comprise a plurality of sections of stacked laminations, separated by non-magnetic spacer members for obtaining a predetermined electrical characteristic. For example, leg portion 16 includes stacked sections 28, 30, 32 and 34, separated by spacer members 36, 38 and 40. The spacer members may be formed of any suitable non-magnetic, non-metallic material which will maintain the desired gap, such as the laminated cellulosic materials. The number of gaps in the magnetic circuit will, of course, depend upon the particular reactor design.

In order to hold the various stacked sections 28, 30-, 32 and 34 in the desired assembled relation, to form the leg portion 16, lock plates 42 and 44 are disposed the length of the leg portion, adjacent to and contacting the outer laminations of each stack. Each stack of laminations has at least one opening through the stack, disposed perpendicular to the joints formed between the adjacent stacked laminations and similar openings are provided in the lock plates 42 and 44 which are aligned with the openings in the stacks of laminations. This allows clamping means such as nut and bolt combinations 46, 48, 50 and 52 to be inserted through the aligned openings to clamp the laminations into a coherent rigid structure. However, as hereinbefore described, when conventional solid spacer members are utilized, the problem of obtaining a spacer member which will support all of the laminations, and still allow the clamping means to exert the desired pressure on the laminations, is critical. Manufacturing tolerances on the spacer dimensions, as well as on the build dimension of the stacked laminations, makes it difficult and impractical to obtain the desired rigidity at each stacked section, resulting in a magnetic core which produces a high sound level when energized.

This invention successfully solves this problem, substantially reducing the sound level of the magnetic core structure by utilizing a spacer member whose dimension in a predetermined direction 'will decrease when the clamping force is applied thereto, without changing the gap spacing. This change in the dimension of the gap spacer allows the force produced by the clamping means to be applied to the stacks of laminations. In describing the gap spacer, leg portion 14 of iron core reactor 10 will be referred to, as it shows only one stack of laminations 54, for simplicity, clearly illustrating the placement of gap spacer 56. Leg portion 14 also includes lock plate members 58 and 60, and clamping means, such as nut and bolt combination 62.

Spacer member 56, which is shown in detail in FIGS. 2 and 3, may be constructed of the same material as conventional gap spacers, such as one of the laminated cellulosic plastic material, thus insuring that the predetermined gap dimension G will be stable. The dimension W of the spacer member 56 is selected to insure that the spacer member is as wide as the lamination buildup, to insure that each lamination in the stack on opposing sides of the spacer member 56 will be supported, preventing it from slipping out of alignment with the other laminations in the stack. The dimension L is not critical, being selected to correspond approximately to the width of the strip material from which the laminations are formed which make up the stack 54, or the width of the adjacent lock plate members. Instead of the spacer member 56 being solid, however, the spacer ,member 56 is formed such that its dimension W, which is perpendicular to the plane of the stacked laminations, or perpendicular to the joints formed between adjacent stacked laminations, and parallel to the direction of force applied to the laminations 54 by clamping means 62, will be reduced when a clamping force is applied thereto. There are many diiferent ways in 'which spacer member 56 may be made flexible or springy in the direction of its dimension W, with FIGS. 2 and 3 illustrating a method in which the conventional spacer member may be made flexible in the direction of its W dimension. Parallel slots or openings 64 and 66 are formed in the spacer member 56, starting at opposite sides of the spacer member 56 on its W dimension and proceeding for a predetermined distance towards the opposite side. By forming the slots 64 and 66 at a predetermined oblique angle to the W dimension, the L dimension sides will remain substantially parallel as the W dimension is reduced.

Thus, spacer member 56 has an unstressed dimension W which is. sufficient to support every lamination in the two stacks of laminations it separates, and it also allows clamping means 62 and lock plates 58 and 60 to corn press its W dimension, and allow substantially all of the force provided by the clamping means to be applied or transmitted to the laminations. The laminations are, thus, clamped into a rigid stack, forming a rigid leg portion which when assembled into an iron core reactor and energized, will produce a substantially lower sound level than the magnetic core construction utilizing the conventional spacer members. Further, this procedure is effective on reactors rated over 600 kva., as well as on smaller reactors. For example, a 1000 kva. reactor constructed with spacer members formed according to the teachings of this invention had a 14 db reduction in sound level on the db 40 scale, over a similarly rated reactor constructed with conventional spacer members.

FIG. 1 illustrates an iron core reactor 10 having le'g members with a rectangular cross-section and lock plates disposed only external to the stacked laminations. The teachings of the invention are equally applicable to reactor legs having a cruciform cross-section, and to reactors which not only have external lock plates, but additional lock plates disposed at spaced intervals across the lamination build which make up each of the stacked sections.

FIG. 4 is a cross sectional view taken across a leg portion 70 of an iron core reactor, between the spacer members and one of the stacks of laminations it separates. Leg portion 70 has a cruciform cross-section, outer lock plate members 72 and 74, and a plurality of additional lock plate members 76, 78, 80, 82 and 84, which are disposed at predetermined intervals through the lamination buildup. Lock plate members 72, 74, 76, 78, 80, 82 and 84 extend through each of the plurality of stacks which make up the complete leg portion 70, thus requiring a plurality of spacer members 86, 88, 90, 92, 94 and 96, each disposed between a pair of adjacent lock plates. The spacer members provide a predetermined non-magnetic gap between the magnetic core section 100, which includes a plurality of stacked laminations 102, and a section which is disposed over the spacer members. The magnetic core section has an opening disposed therein which is perpendicular to the plane of the laminations 102 or perpendicular to the joints formed by the stacked laminations. The plurality of lock plate members also each have openings therein, with an opening in each lock plate member being in substantial registry with an opening in each core section. Clamping means, such as bolt 104 and nut 106, provide the clamping force for clamping the core section 100 into a rigid member. FIG. 4 is partially cut-away to illustrate an insulating tube 108, which prevents bolt 104 from contacting the laminations 102, and Washer members and 112, which separate the head of the bolt 104 and nut 106 from the outer lock plate members 74 and 72.

FIG. 4 illustrates another spacer member configuration which may be utilized, with the spacer member also shown separately in FIGS. 5 and 6. The spacer member 120, shown in FIGS. 5 and 6, is especially suitable for leg members having a cruciform crosssection, and which have a plurality of external and internal lock plates. The plurality of lock plates demand a spacer member which has a W dimension that is small compared with the L dimension, and the different widths of the locking plates allows one of the sides which is parallel to the L dimension to be smaller than its opposite side. The configuration of the spacer member 120 shown in FIGS. 5 and 6 requires that its W dimension be small compared with its L dimension, in order for it to have the desired flexibility, and the sides of the spacer member 120 which are parallel to its L dimension may be cut to fit the width of the adjacent lock plate.

Thus, in the arrangement shown in FIG. 4, each spacer member is formed to have a dimension W which will support all of the laminations in the portion of the stacks it is to separate, and to have sides which are parallel to its L' dimension which are substantially the same length as the adjacent lock plate members. When the nut and bolt, 104 and 106, are tightened, the spacer members 86, 88, 90, 92, 94 and 96 each flex, to allow the force from the nut and bolt to be applied directly to the stacked laminations, producing a tightly clamped rigid core structure, which has a substantially lower sound level when built into an iron core reactor and energized, than core structures utilizing conventional spacer members.

While the invention has been illustrated and described relative to iron core reactors, it will be obvious that the teachings of the invention are equally applicable to any gapped magnetic core structure for electrical inductive apparatus, such as certain types of autotransformers.

A gapped magnetic core structure constructed according to the teachings of the invention has many advantages. The spacer members are easily manufactured, low in cost, and the tolerance on the spacer dimension which supports the laminations is not critical. The spacer members support all of the laminations in the adjacent stacks, eliminating the possibility of laminations slipping out of place. Further, the spacer members flex when a clamping force is applied thereto, without changing the gap dimension, to allow the clamping means to direct its force into the laminations, to tightly clamp the laminations into a rigid, coherent structure, which has a substantially lower sound level than structures formed from conventional spacer members. Further, the gap length may be readily changed by substituting different spacer members, unlike the procedure which involves bonding the ends of the laminations to the spacer member.

Since numerous changes may be made in the above described apparatus and different embodiments of the invention may be made without departing from the spirit the-reof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative, and not in a limiting sense.

We claim as our invention:

1. A magnetic core comprising a plurality of stacks of metallic laminations arranged to form a magnetic circuit; said stacks of laminations having a predetermined build dimension perpendicular to the major planes of said stacked laminations; at least one spacer member having predetermined thickness, width and length dimensions; said at least one spacer member having at least two spaced contact surfaces connected by a flexible intermediate portion which allows the width dimension to decrease when stressed; the unstressed width dimension of said at least one spacer member being at least as large as the build dimension of said stacks of metallic laminations; said at least one spacer member being disposed between two of said stacks of metallic laminations, with its thickness dimension separating said stacks, the major planes of the stacked laminations being substantially perpendicular to said spacer member, and the width dimension of said spacer member being substantially perpendicular to the major planes of said stacked laminations; and, means applying a force to said stacked laminations in a direction perpendicular to the major planes of said stacked laminations, reducing the width dimension of said spacer member and allowing the force to be applied to said stacked laminations.

2. The magnetic core of claim 1 wherein the means applying the force to said stacked laminations includes lock plate members disposed adjacent at least the outer laminations of said stacks of metallic laminations, and clamp ing means.

3. The magnetic core of claim 1 including at least one additional lock plate member disposed between certain of the laminations of the stacked laminations, and at least one additional spacer member; said spacer members being disposed between adjacent pairs of lock plate members, with their width dimensions extending between the lock plate members.

References Cited by the Examiner UNITED STATES PATENTS 1,549,525 8/1925 Cooney 336-6O 2,494,180 1/1950 Koubek 336-100 2,912,659 11/1959 Foster 336- 2,920,296 1/1960 Neurath 336- LEWIS H. MYERS, Primary Examiner. T. J. KOZMA, Assistant Examiner. 

1. A MAGNETIC CORE COMPRISING A PLURALITY OF STACKS OF METALLIC LAMINATIONS ARRANGED TO FORM A MAGNETIC CIRCUIT; SAID STACKS OF LAMINATIONS HAVING A PREDETERMINED BUILD DIMENSION PERPENDICULAR TO THE MAJOR PLANES OF SAID STACKED LAMINATIONS; AT LEAST ONE SPACER MEMBER HAVING PREDETERMINED THICKNESS, WIDTH AND LENGTH DIMENSIONS; SAID AT LEAST ONE SPACER MEMBER HAVING AT LEAST TWO SPACED CONTACT SURFACES CONNECTED BY A FLEXIBLE INTERMEDIATE PORTION WHICH ALLOWS THE WIDTH DIMENSION TO DECREASE WHEN STRESSED; THE UNSTRESSED WIDTH DIMENSION OF SAID AT LEAST ONE SPACER MEMBER BEING AT LEAST AS LARGE AS THE BUILD DIMENSION OF SAID STACKS OF METALLIC LAMINATIONS; SAID AT LEAST ONE SPACER MEMBER BEING DISPOSED BETWEEN TWO OF SAID STACKS OF METALLIC LAMINATIONS, WITH ITS THICKNESS DIMENSION SEPARATING SAID STACKS, THE MAJOR PLANES OF THE STACKED LAMINATIONS BEING SUBSTANTIALLY PERPENDICULAR TO SAID SPACER MEMBER, AND THE WIDTH DIMENSION OF SAID SPACER MEMBER BEING SUBSTANTIALLY PERPENDICULAR TO THE MAJOR PLANES OF SAID STACKED LAMINATIONS; AND, MEANS APPLYING A FORCE TO SAID STACKED LAMINATIONS IN A DIRECTION PERPENDICULAR TO THE MAJOR PLANES OF SAID STACKED LAMINATIONS, REDUCING THE WIDTH DIMENSION OF SAID SPACER MEMBER AND ALLOWING THE FORCE TO BE APPLIED TO SAID STACKED LAMINATIONS. 